More diverse ant colonies raise more offspring

The queen, workers, and larvae are all common black ants Lasius niger. Credit: Romain Libbrecht, JGU
Higher levels of genetic diversity in ant colonies are more successful than those with more closely related genetic backgrounds. This conclusion is from an experiment in which researchers compared different colonies of common black ants.

The study was led by Dr. Romain Librecht, Johannes Gutenberg University Mainz (JGU). Colonies that are more diverse than their neighbors raise more larvae to maturity, it seems. This study could explain why some unusual phenomena such as colonies that have multiple queens and colonies fertilized at once may have occurred in insect societies. This is not just a phenomenon that occurs in ants, but also in many other species of eusocial insect.

Many Eusocial insects are genetically related to one another.

Genetic relatedness is a key factor in the evolution and maintenance of altruistic behavior in the animal kingdom. Social insects such as bees, ants, and wasps have a unique situation where female workers give up their reproductive functions to raise the queens' brood. This division of labor in reproductive reproduction was possible because queens are often fertilized by one male, and all subsequent offspring are the result. Libbrecht noted that most eusocial insect species have colonies that share close genetic similarities, which presumably facilitates collaboration.

Other strategies are possible. There are other strategies. For example, a honeybee queen may mate with up 20 drones while an Argentine ant nest (Linepithema humile), can have as many as 60 queens. However, genetic diversity can come at a cost. Libbrecht said that queens may be at greater risk when they mate with multiple males and that there could be more conflict among workers in certain situations. These strategies were favoured by natural selection and therefore must have certain benefits. Evolutionary biologists have tried to prove the benefits of genetic variety for the past two decades.

The queen, workers, and larvae are all common black ants Lasius niger. Credit: Romain Libbrecht, JGU

"We chose to adopt a different approach to discover how increased genetic diversity confers advantages to insect societies," stated Libbrecht, head the JGU research group Reproduction, Nutrition, Behavior in Insect Societies. His team conducted an experiment in which they controlled the worker force of black garden ants (Lasius nuiger) using a modified version of their experimental study. This species can be found all over Central Europe, including on balconies, in gardens, fields, and near the edges of forests. A colony will usually have one queen, which is why they mate with one male to ensure that their offspring are all of the same genetic background. Libbrecht and his crew collected ants from the region around Mainz. They divided them into two groups. One group was made up of ants that were collected in one colony and the other consisted of ants that were collected in three colonies. Libbrecht explained that they collected pupae as queens wouldn't accept foreign worker ants.

Marina Psalti, the lead author of the article, stated that "this meant that the worker bees that emerged from our test colonies' pupae were not at all related with their queens." This was done to eliminate any possible maternal effects.

Higher genetic diversity in ant colonies results in more larvae

Libbrecht's evolutionary biologists discovered that there was a greater variety among workers which resulted in a higher production of larvae. The two groups produced the same number of eggs. This meant that the groups with more workers were able to produce more larvae, despite having the same number of eggs. According to Libbrecht a small colony in natural conditions can be vulnerable during its initial stage. The speed at which a large number of worker ants can added will determine if it can establish itself.

Colonies made up of different ants may perform better because there is a better division of labor. Certain workers are better at caring for the larvae. They need to be fed, and groomed. Some workers may be better at finding food than others. We conclude that there are benefits to having a variety of workers in ant colonies," Libbrecht summarized his findings.

Continue reading A study on ants offers information about the evolution of social insects

Marina N. Psalti and colleagues, Experimental increase in worker diversity benefits brood productivity in ants, BMC Ecology and Evolution (2021). Information from the Journal: BMC Ecology and Evolution Marina N. Psalti et.al, Experimental increase in worker diversity benefits broodproduction in ants. (2021). DOI: 10.1186/s12862-021-01890-x

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